Fingerprints of Through-Bond and Through-Space Exciton and Charge π-Electron Delocalization in Linearly Extended [2.2]Paracyclophanes

J Am Chem Soc. 2017 Mar 1;139(8):3095-3105. doi: 10.1021/jacs.6b12520. Epub 2017 Feb 21.

Abstract

New stilbenoid and thiophenic compounds terminally functionalized with donor-donor, acceptor-acceptor, or donor-acceptor moieties and possessing a central [2.2]paracyclophane unit have been prepared, and their properties interpreted in terms of through-bond and through space π-electron delocalization (i.e., π-conjugations). Based on photophysical data, their excited-state properties have been described with a focus on the participation of the central [2.2]paracyclophane in competition with through-bond conjugation in the side arms. To this end, two-photon and one-photon absorption and emission spectroscopy, as a function of temperature, solvent polarity, and pressure in the solid state have been recorded. Furthermore, charge delocalization through the [2.2]paracyclophane in the neutral state and in the oxidized species (radical cations, dications and radical trications) has been investigated, allowing the elucidation of the vibrational Raman fingerprint of through-space charge delocalization. Thus, a complementary approach to both "intermolecular" excitation and charge delocalizations in [2.2]paracyclophane molecules is shown which can serve as models of charge and exciton migration in organic semiconductors.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.